What to put in my duck run?

[TripleAAA]

Hi All!
So I live in Southeast Alaska. We get an insane amount of rain... Like way way way more then Seattle. I have just about finished my duck run, and have come to a indecision. My yard is all gravel, all the way down to the bedrock. It still has drain issues, so I built my run with a tall frame around the bottom. I then filled with rocks and then gravel on top of that. I now have about 7 inches of space to fill with what ever I decide to finish off the run with. Half of the run has a roof over it so they can get out of the driving rain if they want with out going in their house. The other half is open to the elements and also will have a raised pond for them to swim in. I was planning on using sand as the final layer, but now like I said am not sure. The internet it seems is about 50/50 on each side of whether it is good or not.
We use our yard a lot and want the ducks to not stink it all up and drive us out of there or make our neighbors mad... and do not want to end up with a muddy mess. Plus my daughter is very allergic to hay so thats out. And everything has to be shipped in by barge because we live on an island which drives prices up pretty far.
I'm not apposed to bringing in some soil. I could put some weed barrier on top of the gravel and then the dirt so they don't mix and the drainage would hopefully work......
thanks in advance!

 

[Amiga]

I have found that duck manure mixes in with the base material. Always.

It can form a nearly impermeable layer over gravel after a time.

So having the pen on a 2% slope makes a big difference - excess water will run out of the pen.

Where you are, you might be able to grow flax or find someone who does and use that for the base - it mixes with manure and you can use it to mulch garden beds.

I use chopped straw over soil in the day pen. Occasionally I stir it with a cultivator, but otherwise I only have to pull material out once or twice a year because it builds up and I bump my head on the overhead fencing. It's great stuff for the garden. The pen is on a 2% slope. I have pea gravel and sand under the swim pans. That section seals up with the manure and so I am very glad for the slope. I dug a shallow channel to direct the water into garden beds. No ugly smell, the plants love it.

High-carbon material mixed with manure, moist but not sodden, should prevent ugly odors. But if the manure stays wet it will release unpleasant aromas.

Oak leaves are wonderful around the swim pan area to reduce odor.

 

[TLWR]

I don't think you will need to worry about smell. When I lived in Kodiak, the rain would have easily diluted the poop and kept the smell down.

What is easier for you to get - sand or dirt?
Maybe do sand in the covered part and that can be raked fresh as needed. Dirt will allow for more bugs to be in the dirt over being in stand and then when they drill, they will find more goodies. But with dirt and rain, you will have mud.